The leading cause of death from gastrointestinal disease in neonates is necrotizing enterocolitis (“NEC”; as reviewed in reference 51). 90 percent of the cases of NEC occur in premature infants (51). Over forty years of research have unfortunately made relatively little progress towards improving the prognosis of patients with NEC (3), which, after surgical treatment, bears a survival rate of only approximately 50% (4).
One area of recent development is the discovery that a class of bacterial receptors named Toll like receptors (“TLR's”) play an essential role in the pathogenesis of NEC. Of particular importance is TLR4, the receptor for lipopolysaccharide (LPS), which is the outer membrane component of gram negative bacteria (12). It has been found that (i) mice with mutations in TLR4 are protected from the development of NEC (22); (ii) TLR4 signaling regulates the balance between injury and repair in the newborn intestine (21); and (iii) TLR4 is increased in the intestinal mucosa of mice, rats and humans with NEC compared to controls (21, 23). TLR4 activation appears to not only promote intestinal injury, but also reduces the ability of the mucosa to heal. It has been postulated that that prematurity, hypoxia and endotoxemia, each of which are linked to NEC, result in persistent upregulation of intestinal TLR4 and consequent disease (21). Therapeutic approaches to NEC have been developed that involve inhibiting activity of TLR4. For example, see U.S. Pat. No. 8,188,058 by Hackam.
Modulation of other TLRs may also be used therapeutically. Activation of TLR9, the enterocyte receptor for bacterial DNA (which, unlike mammalian DNA, is rich in CpG groups and significantly hypomethylated) with CpG-DNA led to reduced TLR4 signaling both in vitro and in newborn's intestine (U.S. Pat. No. 8,188,058 by Hackam and 40). The potential use of oral CpG-ODNs in asthma has been explored (53).